[Footnote 1: See Insectivorous Plants, by Charles Darwin. New York: D.
Appleton and Co., 1875.

How Plants Behave, Chap. III.

A bibliography of the most important works on the subject will be found in
Physiological Botany, page 351, note.]

[Footnote 2: Reader in Botany. XV. Insectivorous Plants.]


5. _Respiration_.--Try the following experiment in germination.

Place some seeds on a sponge under an air-tight glass. Will they grow?
What causes them to mould?


Seeds will not germinate without free access of air. They must have free
oxygen to breathe, as must every living thing. We know that an animal
breathes in oxygen, that the oxygen unites with particles of carbon within
the body and that the resulting carbonic acid gas is exhaled.[1] The same
process goes on in plants, but it was until recently entirely unknown,
because it was completely masked during the daytime by the process of
assimilation, which causes carbonic acid to be inhaled and decomposed, and
oxygen to be exhaled.[2] In the night time the plants are not assimilating
and the process of breathing is not covered up. It has, therefore, long
been known that carbonic acid gas is given off at night. The amount,
however, is so small that it could not injure the air of the room, as
is popularly supposed. Respiration takes place principally through the